Fluid treatment device

ABSTRACT

A device for the treatment of an influent with a porous media. The influent passes radially through the porous media and into an internal volume of the device. The treated influent then passes through an open check valve in the internal volume, and then to downstream equipment. During a backwash operation, a backwash fluid is passed into the internal volume of the device in a direction to close the check valve. The blocked path in the internal volume of the device causes the backwash fluid to pass radially outwardly into the porous media and fluidize the same.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of prior U.S. application Ser. No.11/053,550, filed Feb. 8, 2005, now U.S. Pat. No. 7,163,621 whichapplication is a continuation of prior U.S. application Ser. No.09/978,962, filed Oct. 15, 2001 (now U.S. Pat. No. 6,852,232), which isa continuation of application Ser. No. 09/194,060, filed Nov. 20, 1998(now U.S. Pat. No. 6,322,704), which is a national stage application ofPCT/US97/08942 filed May 23, 1997, which is a PCT InternationalApplication which claims the benefit of U.S. Provisional ApplicationNos. 60/018,168 filed May 23, 1996, and 60/023,679 filed Aug. 17, 1996.The subject matter of all the foregoing applications is incorporatedherein by reference.

TECHNICAL FIELD OF THE INVENTION

This present invention relates in general to a device for coacting aporous media with an influent, or for removing impurities, solids orparticulate matter from the influent, and more particularly to aradial-flow type of filter having a nonbonded filter media, and in whichthe flow of the fluids can be reversed in a backwash operation to removethe filtered matter and thus regenerate the filter for reuse.

BACKGROUND OF THE INVENTION

While there exists many types of filters for removing particulate matterfrom an influent, such filters are generally classified as the typehaving a bonded or nonbonded media. A bonded media filter includes aremovable cartridge element constructed of a fibrous woven or nonwovenmaterial. The material can be selected with a given porosity so thatparticulate matter of a given size can be removed from the influent.When the bonded cartridge filter element has a sufficient accumulationof filtered matter thereon, it is simply removed and cleaned, orreplaced. The cartridge type filters are not easily backwashed. However,many cartridge-type filters are of the radial-flow type, whereby amaximum surface area is provided for filtering, thereby allowing areduced resistance to the flow of the influent.

Another family of filters contains a nonbonded media, such as sand,glass beads, diatomaceous earth and other granules or particles throughwhich the influent flows. The nonbonded media is generally of a granulartype of material, circular, rounded or irregular in shape so that thespacing between the particles is effective to filter the particulatematter. The advantage of utilizing a nonbonded media filter is that itcan be backwashed to regenerate the media. Backwashing can include thefluidizing of the media which allows the fluid to dislodge the entrappedcontaminants from both the interstices between the grains of the media,as well as from the surface of each grain itself. The primarydisadvantage of such type of filter is the size requirements and costs,as well as filter inefficiencies, in that they have little surface areaof the filter exposed to the incoming flow, and thus are forced toutilize larger media grains and higher flow rates per unit area exposedto the incoming flow. In other words, the development of a radial-flow,nonbonded media filter that can be regenerated by backwashing is not asimple task.

In U.S. Pat. No. 3,415,382, by Martin, there is disclosed a radial-flowfilter utilizing glass beads as the nonbonded media. While such filteris effective for its intended purpose, it utilizes a rather large-sizebead media and can not be regenerated without disassembly.

Radial-flow filters have a broad range of applications in themanufacturing or process industries which require the removal ofimpurities or solids from an influent. A generalized diagram of a basicradial-flow filter 10 is shown in FIG. 1. The filter consists of twoconcentric perforated pipes 12 and 14 and a porous filter media 16filling the annular space 20 between the two pipes, all housed within afilter case 18. The porous media 16 is composed of tiny glass sphereswhich are of uniform size for a particular filter but can range widelyin size for different filters. The spheres can be submicron sized,micron sized or as large as coarse sand, and completely fill thecompartment 20 between the perforated pipes 12 and 14. The perforationsin the pipes are circular, of uniform size and arrayed in a uniformpattern, but it can be of other arrangements. Theconcentric-pipes-porous-medium assemblage is encased so that fluidcompletely surrounds the assemblage during filtration. Filtration takesplace along the entire axial length of the filter 10 as the fluid flowsradially into the porous media 16 through the perforations in the outerpipe 12, and exits the porous media 16 through the inner perforated pipe14. The impurities are trapped as the fluid traverses the porous media16.

The porous media 16 must be cleaned by backwashing after one or morefiltration cycles. Backwashing consists of surges of clean fluid thatflows radially outwardly from the inner pipe 14, into the porous media16 and out through the outer perforated pipe 12. The direction of flowis basically opposite to that which takes place during filtration. FIG.2 shows the filter 10 during a conventional backwash cycle. Therelatively high fluid velocities and surges that are generated aroundthe glass spheres dislodge and flush out the accumulated impurities. Theimpurities are sufficiently small to pass through the spaces between theglass spheres that comprise the porous media 16. However, not all of theimpurities are able to be dislodged as a gum residue and particlesgradually build up in the porous media 16. Therefore, after a number offiltration backwashing cycles, the filter 10 must be disassembled toreplace or recondition the porous media 16.

From the foregoing, it can be seen that a need exists for a radial-flowfilter of the type employing a nonbonded media, and constructed so thatbackwashing capabilities are afforded. Another need exists for anonbonded media filter constructed such that during the backwashingcycle, the porous media is completely regenerated, thereby eliminatingthe need to periodically disassemble the filter and completely clean thesame or replace the porous media. Another need exists for a nonbondedmedia filter of the type that can be backwashed, and where thebackwashing pressures need not be excessive. Another need exists for afilter of the type where the end of a backwash operation results in ahigh restriction to the flow of the backwash liquid, thereby increasingthe pressure of the liquid and signaling that the backwash operation iscomplete.

SUMMARY OF THE INVENTION

In accordance with the principles and concepts of the invention,disclosed is a radial-flow device utilizing a porous media and which canbe efficiently backwashed to dislodge the impurities and particulatematter to thereby regenerate the porous media. According to a preferredembodiment of the invention, the radial-flow device includes anover-sized media chamber for the granular filter beads. During abackwash cycle, the reverse flow of the backwash liquid provides anupward lifting force on the granular beads and transfers the beads intoan upper portion of the chamber, thereby separating the beads andallowing accumulated particulate matter to be dislodged and carriedaway. During the treatment cycle, the granular beads settle to thebottom of the media chamber so that the influent flows between the beadsto filter the particulate matter therefrom.

In accordance with the preferred embodiment of the radial-flow filter,the influent passes through the screen mesh covering the outerperforated cylinder and radially through the filter granules. Thefiltered influent then passes through an inner screen mesh-coveredperforated cylinder. The filtered influent then passes through a seriesof open check valves located within the mesh-covered inner perforatedcylinder, and then to the outlet port of the filter.

During the backwash cycle, the backwash liquid is forced through thefilter in a reverse direction, whereby the check valves are closed andthe backwash liquid is directed in a reverse direction through thegranular media. In the backwash operation, the liquid may generally passthrough the granular filter media in a radial direction, and in anupward axial direction. The upward force of the backwash liquid causesthe check valves to close, thereby forcing a majority of the liquid intothe granular filter media rather than upwardly through the innerperforated cylinder. The upward or drag force of the backwash liquidcauses an upper section of the granules to be lifted into a backwashchamber where the particulate matter is separated therefrom and carriedout of the filter. This movement and separation of the granular media issometimes denoted herein as “fluidization,” and occurs when the dragforce exceeds the buoyant weight of the upper layer or section of thegranular media. Once the upper filter section has been fully fluidized,then the subsequent underlying section also becomes fluidized, wherebythe section of granular media is forced upwardly so as to be separatedand the particulate matter released therefrom. Each underlying sectionof the filter is sequentially fluidized to thereby regenerate the filtermedia during the backwash cycle. Because each filter section issequentially fluidized, the backwash pressure is significantly reduced,thereby easing the requirements of backwash pumps, equipment and thelike.

In the preferred embodiment of the invention, disclosed is a method oftreating an influent, including the steps of passing the influentradially inwardly through a porous media to treat the influent, andpassing the treated influent into an internal volume that is surroundedby said porous media. The treated influent is then passed through anopen check valve located in the internal volume, and then the treatedinfluent is coupled from the treatment device to downline equipment.

Other embodiments of the invention include different arrangements, suchas O-rings, perforated bladders and check valves for enhancing thefluidizing of the filter media.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages will become apparent from the followingand more particular description of the preferred and other embodimentsof the invention, as illustrated in the accompanying drawings in whichlike reference characters generally refer to the same parts, elements orcomponents throughout the views, and in which:

FIG. 1 is a generalized cross-sectional view of a radial-flow filterwell known in the prior art, showing the liquid flow during a filtrationcycle;

FIG. 2 illustrates the radial-flow filter of FIG. 1, but during abackwash cycle;

FIGS. 3 and 4 illustrate in generalized form the structural features ofthe radial-flow filter assembly constructed in accordance with theinvention, during a respective filtration cycle and during a backwashcycle;

FIGS. 5 a-5 f are generalized sectional views of a portion of aradial-flow filter showing the different stages of the fluidization ofthe granular filter media;

FIG. 6 a is a partial cross-sectional view of a portion of a radial-flowfilter showing velocity vectors that act upon the granular filter mediato produce an upward drag force to thereby cause fluidization of thegranular media;

FIG. 6 b is a partial cross-sectional view of a radial flow filterequipped with O-rings between the housing and the outer perforatedcylinder, with velocity vectors showing the drag forces on the filtermedia;

FIG. 7 is a computer generated drawing of the liquid flow pattern duringa backwash operation;

FIG. 8 is a cross-sectional view of one embodiment of a radial-flowfilter provided with the backwash and fluidizing capabilities of theinvention;

FIG. 9 is a cross-sectional view of a check valve of one embodimentemployed in the inner perforated cylinder;

FIG. 10 is a top view of a check value plate constructed in accordancewith a second embodiment;

FIGS. 11 and 12 are cross-sectional views of a check valve in respectiveclosed and open positions, as utilized in the case that houses thefilter assembly;

FIG. 13 is a cross-sectional view through different portions of aradial-flow filter constructed in accordance with another embodiment ofthe invention;

FIGS. 14 a and 14 b are generalized cross-sectional views of a radialflow filter constructed in accordance with another embodiment of theinvention, illustrating a perforated bladder in a filter cycle and in abackwash cycle; and

FIGS. 15 a and 15 b are generalized cross-sectional views of a radialflow filter constructed in accordance with yet another embodiment of theinvention, showing a radial flow filter operating in an inverted manner.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 3 illustrates in a generalized diagrammatic form, the radial-flowfilter assembly 50 constructed in accordance with the invention. Theradial-flow filter assembly 50 employs a new backwashing technique,thereby avoiding the downtime and expense of reconditioning thenonbonded porous media, as was periodically required by the prior artfilters. While the preferred and other embodiments will be described inconnection with a device using a granular filter media for filteringparticulate matter from an influent, the principles and concepts of theinvention can be utilized for coacting a media with an influent, a gasor liquid, where the media periodically requires backwashing to cleanseor regenerate the media.

The radial-flow filter assembly 50 is constructed with a rigidcylindrical housing 52 that extends the entire length of the filterassembly. An inner perforated cylinder 54 with a screen mesh extends theentire length of the filter housing 52. While not shown, the innerscreen mesh is formed onto the perforated cylindrical support structure54 for preventing collapse of the screen mesh. The volume in which theporous media 56 is contained includes two chambers. During thefiltration cycle, the porous media 56 is situated in a first chamber 58located generally in the lower or bottom part of the filter assembly 50.The first porous media chamber 58 comprises an annular area bounded byconcentric screen mesh cylinders, one defining the inner screen mesh 54and the other defining an outer cylindrical screen mesh 60. Much likethe inner screen mesh cylinder 54, the outer screen mesh 60 is supportedby a perforated cylindrical pipe that extends axially only about halfwaythrough the filter assembly 50. The size of the pores in the screen meshcylinders 54 and 60 is smaller than the general dianetric size of theporous media 56. In this manner, the screen mesh contains the porousmedia within the filter 50.

As noted in FIG. 3, and in accordance with an important feature of theinvention, the radial flow filter assembly 50 includes an upper backwashchamber 62 of a volume that is preferably about the same as that of thelower chamber 58. As will be described more fully below, the generaldiameter of the top backwash chamber 62 is greater than that of thebottom porous media chamber 58 to facilitate fluidizing, separation andagitation of the porous media 56 during the backwash cycle. Fixed withinthe inner perforated cylinder 54 and screen mesh is a plug 64 thatprevents the passage of the influent axially from the top portion of thescreen mesh cylinder to the bottom portion of the screen mesh cylinder,and vice versa. One or more orifices, one shown as reference numeral 66,are fixed at spaced-apart locations within the inner perforated cylinder54. The size of each spaced-apart orifice is smaller so that thebackwash flow of liquid therethrough toward the plug 64 becomes morerestricted. As will be described below in conjunction with the backwashcycle, the orifices 66 force the backwash liquid outwardly into theporous medium 56 to thereby provide a lifting function for fluidizingvertical sections of the porous media.

In the filtration cycle, a small portion of the influent with suspendedparticulate matter enters the top of the inner perforated cylinder 54and flows radially through the screen mesh and down the top backwashchamber 62, as noted by arrows 68. This flow of influent facilitates thedownward transport of any porous media 56 that may have hung up in thebackwash chamber 62 during a backwash cycle. However, a majority of theinfluent flows through plural ports 70 located in the housing 52 and isdirected around the outer perforated cylinder 60. While not shown inFIGS. 3 and 4, the filter assembly 50 is housed in yet another housinghaving inlet and outlet piping coupled to other pumping equipment. Theports 70 each include a check valve for allowing the entry of theinfluent into the filter assembly 50, but prevent an opposite flow ofbackwash liquid. The influent passes through the outer perforatedcylinder 60 and radially through the porous media 56 where theparticulate matter becomes lodged within the interstices of the porousmedia, as well as to the surface of the porous media 56 itself. Theinfluent is thus filtered. The filtered liquid passes through themesh-covered inner perforated cylinder 54 and flows downwardly thereinthrough the orifices 66. The filtered liquid exits the radial flowfilter assembly 50 as shown by arrow 72.

The porous media may be glass or other types of beads, sand,diatomaceous earth, activated carbon, anthracite coal or any othergranular media that has the desired characteristics for removingparticulate matter of a specified size or impurities of a specifiedtype. It is well known that beads of a nominal diameter of 100 microns,when tightly settled together as shown in FIG. 3, can filter particulatematter much smaller than the size of the beads. Hence, the mesh screencovering the perforated cylinders 54 and 60 contains the beads, butallows the particulate matter to flow therethrough and become lodged andfiltered by the media bed. Depending upon the amount of particulatematter suspended in the influent being filtered and the volume of theporous media 56, the interstices thereof eventually become full of theparticulate matter, thereby reducing the efficiency of the filterassembly 50 and increasing the load on the pump.

In accordance with an important feature of the invention, theradial-flow filter assembly 50 can be efficiently backwashed byreversing the flow of liquid therethrough. The flow of the backwashliquid is shown in FIG. 4. The backwash liquid enters the radial-flowfilter assembly 50 at the location shown by arrow 74. The backwashliquid attempts to flow through the inner perforated cylinder 54 in anaxial direction, but due to the series of smaller orifices 66, the flowis directed outwardly into the porous media 56. It is noted that thecheck valve at the port 70 is forced closed during the backwashoperation, thereby directing all of the backwash liquid upwardly in thefiltration chamber 58.

In accordance with an important feature of the invention, an upperportion of the porous media 56 is first fluidized, as shown in FIG. 4,due to the uplifting drag force exerted thereon by the backwash liquid.In addition, the size of the different orifices 66 allow sections orstages of the porous medium 56 to be fluidized in a sequential manner.It is noted that the top portion of the porous media 56 becomesfluidized first, because the lifting force thereon is greater than thebuoyant weight of the layer of the upper portion of the porous media andparticulate matter accumulated therein. Once the upper section orportion of the porous media 56 becomes fluidized, the weight thereof isremoved from the underlying section of the porous media, whereby suchunderlying section is then fluidized. All of the porous media 56 in thefiltration chamber 58 eventually becomes fluidized, wherebysubstantially all of the filter media is carried by the backwash liquidinto the overlying backwash chamber 62. The sectional fluidizationovercomes the need of a large backwash pressure to lift the entireannular column of the porous media. The lifting of the media column isdifficult to accomplish without a substantial amount of backwashpressure.

The backwash chamber 62 provides two important functions. First of all,the fluidizing of the porous media 56 from the smaller-diameterfiltration chamber 58 is propelled by a swirling action into thebackwash chamber 62. This swirling motion tends to agitate the porousmedium 56 so that it separates and thereby releases the particulatematter. The particulate matter is carried by the backwash liquid throughthe mesh-covered inner perforated cylinder 54 and out of the filterassembly 50 in the direction noted by arrow 76. The upper portion of thefilter housing 52 can be perforated for allowing larger particulatematter and impurities to be carried out of the filter assembly 50. Bychoosing the sizes of the orifices 66 as a function of the volume andpressure of the backwash liquid, and as a function of the size andweight of the porous media 50, the backwash liquid can impart sufficientdrag forces on the sections of the porous medium 56 to lift all of thegranules and transfer the same from the filtration chamber 58 to thebackwash chamber 62. A second feature of this technique is that whensubstantially all of the porous medium 56 has been transferred to thebackwash chamber 62, the flow of the backwash liquid is impeded by theaccumulation of the fluidized porous media around that part of the innermesh-covered perforated pipe 54 that extends into the backwash chamber62. Thus, when fluidization of the porous media 56 is completed, a risein the pressure of the backwash liquid is noted. This can be a signalthat the backwash cycle of the filter assembly 50 is complete andmeasures can be taken to proceed with a filtration cycle.

The increased resistance to the flow of the backwash liquid can beadvantageously utilized when plural radial-flow filters are utilized inparallel. If each of the radial-flow filter assemblies 50 is providedwith a common source of the backwash liquid, then when one filterbecomes completely fluidized and thereby increases the flow of thebackwash liquid therethrough, the pressure of the backwash liquid isthen available to the other filters for facilitating fluidizing of theporous media thereof. In other words, once one filter becomes fluidized,it does not allow a substantial flow of backwash liquid therethrough,but substantially impedes the flow therethrough. This can be veryhelpful when one filter of a number of parallel-coupled filters has avery clogged porous media which requires a major amount of the backwashpressure for fluidizing the porous media thereof.

FIGS. 5 a-5 f pictorially illustrate an example of the sequentialfluidizing of the different stages of the porous media 56. Shown is anexemplary radial-flow filter having four check valves 90-95 disposed inthe inner perforated cylinder, thus creating five sections or stages ofthe porous media 56. The check valves are shown in more detail in FIG.9. FIG. 5 a illustrates the annular column of the filter media 56 duringthe initial backwash cycle, just before fluidization of the granularbeads. In FIG. 5 b, the top porous media section 80 begins to becomefluidized and is lifted by the drag forces into the backwash chamber 62.As noted above, this is because the axial drag force exerted on the topportion 80 of the porous media 56 exceeds the buoyant weight of themedia itself, thereby causing the porous media to be forced upwardlyinto the backwash chamber 61. As the process continues, the firstsection 80 of the porous media is completely lifted and directed intothe backwash chamber 62, as noted in FIG. 5 c. In FIG. 5 c, thesubsequent section 82 begins to fluidize and become transported upwardlyto the backwash chamber 62 where it separates from itself, as well asfrom the filtered particulate matter. The second media section 82 islifted at this time in the backwash cycle because the buoyant weight ofthe first or upper section 80 has been removed. In FIG. 5 d, asubsequent section 84 of the porous media 56 begins to fluidize and belifted upwardly to the backwash chamber 62. FIG. 5 e shows thefluidizing of the media section 86. In FIG. 5 f, the bottom-most section88 of the porous media is lifted due to the drag forces exerted thereonby the backwash liquid entering the bottom inlet 96 of the filterassembly.

It is important to note that the check valves 90-94 and 95 each haveorifices of a different size. The top orifice in the check valve 90 hasthe smallest opening therein, the bottom orifice 95 has the largestopening, while the middle orifices of check valves 92 and 94 haveintermediate-size openings. The inlet 96 preferably has no actualorifice structure, but the opening itself functions as an orifice thatis larger than that of the bottom orifice structure 95. The sizes of theorifices are important in the staged fluidizing of the porous media 56.The size of the top orifice in check valve 90 is selected so that, basedon the pressure of the backwash liquid flowing into the inlet 96, thedrag forces imparted to the porous media 56 cause the upper section 80to be lifted. Once the top section 80 of the porous media 56 ishydraulically transported upwardly, the backwash liquid continues toflow through the orifice in check valve 90, unimpeded by the porousmedia 56. However, since the orifice in check valve 90 is somewhatsmall, the remaining force of the backwash liquid directed through theintermediate orifice in check valve 92 imparts a sufficient drag forceto the second section 82 to lift the porous media 56. With the differentsized orifices in check valves 90-95, it is assured that each section ofthe porous media 56 is acted upon by substantially the same drag force,when the section thereabove has been fluidized and moved to the backwashchamber 62. The appropriate size of the orifices can be selected as afunction of the pressure of the backwash liquid, the size and weight ofthe porous media 56, and other parameters, based on trial, error andexperimental techniques. As an alternative, the radial-flow filtersection 50 constructed according to the invention can be modeled andanalyzed by way of appropriate software programs. One such filter fluiddynamics program is identified as Fluent. The radial filter of theinvention was appropriately modeled and the characteristics thereof weredetermined by such program. The results thereof are identified in aPh.D. thesis entitled Process Characteristics of a Radial Flow FilterDuring Backwash, by Miguel Amaya, presented Aug. 17, 1996. Thedisclosure of such thesis is incorporated herein by reference thereto.

As noted above, an important feature of the invention that allowssectional fluidizing of the porous media during the backwashingoperation, is the provision of a series of spaced-apart orifices ofdecreasing radii installed in the inner perforated cylinder 54. Shown inFIG. 6 a is a drawing of the computer analysis of a radial-flow filterstructure utilizing such type of orifices and the effect thereof on theporous media located in the annular area between the inner perforatedcylinder 54 and the outer perforated cylinder 60. A first orificestructure 90 and a second orifice structure 92 are shown fixed withinthe inner perforated cylinder 54. In this embodiment, the innerperforated cylinder 54 has a major internal area thereof covered by abladder 100. The bladder 100 can be a durable sheet-like elastomericmaterial bonded or otherwise adhered to the inner surface of theperforated cylinder 54. The bladder 100 covers the perforations andobstructs the flow of liquid therethrough. A small area 102 ofperforations 104 in the inner perforated cylinder 54 remains uncoveredby the bladder 100 in a location just under the perforated structures 90and 92. As an alternative, rather than employing a bladder 100, theinner cylinder 54 can simply be constructed without being fullyperforated. The flow of the backwash liquid in the inner perforatedcylinder 54 is shown by the arrows 106. The arrows 108 shown in thefiltration chamber 58 illustrate velocity vectors of the backwashliquid.

The orifices 90 and 92 restrict the flow of the backwash liquid in theinner perforated cylinder 54 and give rise to drag forces on the porousmedia. It can be appreciated that the porous media can be displacedaxially upwardly during the backwashing operation, only if the dragforces are greater than the buoyant weight of the porous media itself.The magnitude of the axial components of the liquid velocities identifythe regions where the drag forces can exceed the buoyant weight of theporous media. The velocity vectors 108 of FIG. 6 a illustrate thedynamics of the fluid flow and drag forces at one instant of time. Inthe porous media generally shown in media section 110, the velocityvectors 108 are directed generally in an upward direction. Assuming thatthe top of the porous media is as shown in FIG. 6 a, then the buoyantweight of the porous media is the least at this location, with respectto the drag forces produced thereon as a result of the orifice 90. Bycomputer analysis, it has been determined that by the appropriateselection of the size of the orifice 90, the size and spacing of theperforations 104 in the inner perforated cylinder 54, the size andweight of the porous material, the drag forces can be made to exceed thebuoyant weight of the porous material. In this event, the porousmaterial is lifted upwardly and removed from the filtration chamber 58to the backwash chamber 62.

It is noted in the region 112 of the filtration chamber 58 that thevelocity vectors are substantially zero and there is no net drag forcesexerted on the porous material at such location. The velocity vectors111 just above the region 112 are directed downwardly. This downwardforce on region 112 prevents the entire column of the media from beinglifted as a plug. However, once the upper section of the media aboveorifice 90 has been removed, the downwardly directed vectors becomenonexistent, thus preparing the subsequent media section for fluidizing.Sequential fluidization from the top to the bottom is thus enhanced.With respect to the second orifice 92, upwardly-directed drag forces areexerted on the porous media at section 114. However, due to theaccumulated weight of the porous media situated thereabove, the dragforces do not exceed the buoyant weight of the porous media at section114. When, however, the upper section 110 of the porous media has beenremoved and fluidized, the drag forces at section 114 then exceed thebuoyant weight of the porous material and the granular filter particlesof such section begin to rise and are transferred to the backwashchamber 62 for fluidization. This same type of fluid dynamic actionoccurs with the remaining orifice sections until the entire annularfiltration chamber 58 has been emptied of the porous media.

FIG. 6 b is a partial cross-sectional view of the radial flow filterequipped with an annular band 116, or the like, between the outerperforated cylinder 60 and the housing 52 of the filter assembly. As canbe seen, there is one such annular band associated with each section ofthe porous media 56. The annular band or other type of obstruction,functions to redirect the backwash liquid from the outer annular chamber118 back into the porous media 56. The annular band 116 can beconstructed integral with the inside wall of the filter assembly housing52, or integral with the outer sidewall of the outer perforated cylinder60.

FIG. 7 illustrates the flow of the liquid stream during the backwashoperation. The porous media of the top section has already beentransported by fluidizing. A vertical cross-section of the filter isillustrated, where the inner perforated cylinder is equipped with fiveorifices with decreasing radii. The heavy and darkened areas illustratethe heavy flow of the backwash liquid, while the individual wavy linesshow areas of reduced flow of the backwash liquid. It is noted that inthis illustration, the upper section of the porous media 56 has beenfluidized, while the lower sections of the porous media bed are exposedto drag forces that are less than the buoyant weight of the overlyingmedia, whereby no fluidization is yet occurring. It can thus be seenthat a radial-flow filter can be structured to provide fluidization ofthe porous material without requiring excessively high pressures orotherwise compromising the efficiency of the filtration operation.

As noted above, various structural elements of the radial-flow filteraffect the capability and efficiency of the fluidization process.Amongst the many variables that must be considered in the fluidizationof the porous media, it is noted that the magnitude and effect of theflow rate on both the axial drag force component and the pressure dropis larger than the effect of many of the other variables. By computeranalysis, it was found that a larger drag force was obtained byincreasing the flow rate to the filter, but at the expense of a largepressure drop. The properties and characteristics of the porous mediatend to influence the responses more than changes in the perforationpattern of the inner perforated cylinder 54. As an example, the decreaseof the particle size of the porous media increased the pressure by5955Pa on the average, which is nine times the magnitude of the effectof percent of the perforated open area change of the inner perforatedcylinder 54. The drag force experienced an average increase with respectto the magnitude of the effect of the percent open area increase. Withregard to the design of a radial-flow filter, this suggests that assmaller particle sizes are employed, the type of perforation patternbecomes less critical. It is also noted that changes in the percent openarea have an opposite effect on the drag force. For example, the averageeffect of increasing the percent open area was a decrease in the dragforce, while the effect of increasing the perforation size resulted onthe average, in an increase in the drag force. As also noted with thecomputer analysis, with a high percent open area, large perforations inthe inner perforated cylinder 54 decrease the drag force, while at lowpercent open areas, large perforations increase the drag force.Increases in both the percent open area and the perforation sizeproduced comparable decreases in pressure drop across the radial-flowfilter. It was also noted that the flow rate of the backwash liquid andthe particle diameter of the porous media were found to have the largestinfluence on the drag force and pressure drop in the filter. Theparticular type of perforation pattern becomes less relevant withrespect to the drag force and pressure drop, with higher flow rates andsmaller particle diameters.

In one of the embodiments of the invention, as analyzed by way ofcomputer analysis on the program FLUENT (V4.31), Fluid Flow Modeling,1995, Fluent, Inc., Centerra Resource Park, 10 Cavendish Court, N.H.03766, the filter was structured as follows. Five orifices wereemployed, with radii ranging from 0.254 inches to 1.047 inches. Thegeneral diameter of the granular particles were between 44-840 microns,with a specific gravity of 2.5, which is very similar to that of sand.The radius of the inner perforated cylinder 54 was 0.75 inches, withperforations comprising an open area of sixty-six percent. The annulardimensions of the filtration chamber containing the porous media was0.80 inches (radial) by 22.625 inches (axial). The flow rate or pressureof the liquid media was between 3 gpm to 28 gpm. The backwash pressurewas in the range of 0.5 kPa to 10.0 kPa. With a filter constructed assuch, it is contemplated that the porous media can be successfullyfluidized to thereby completely remove the impurities therefrom andprevent down time by disassembly of the filter or replacement of theporous media.

FIG. 8 illustrates in cross-sectional form a radial-flow filterincorporating many aspects and features described above. The filter 120includes a base 122 and a removable housing 124 coupled thereto by wayof a bolt and clamp arrangement 126. The housing 124 is sealed to thebase 122 by means of elastomeric or other types of seals, not shown. Thebase 122 includes an inlet connection 128 coupled to a supply ofinfluent that is pumped in the direction of arrow 130. The influentincludes impurities which may comprise particulate matter, liquids,etc., that are separated by way of the filtration bed contained withinthe housing 124. Once the impurities are removed, the effluent exits thefilter by way of an outlet connection 132, in the direction of arrow134. In a backwash operation, the backwash liquid is directed into thefilter 120 by way of connection 132, and exits the filter with theimpurities suspended therein by way of connection 128. Different valvingarrangements and control systems are well known to those skilled in theart for disconnecting filters from pumping systems and reconnecting thesame to backwash systems.

Fixed within the housing 124 is a radial-flow filter assembly 136. Thefilter assembly 136 includes an enclosed case 138 for containing andsupporting therein the filter parts and components. The case 138includes a cylindrical sidewall 140 fixed between a top end cap 142 anda bottom end cap 144. The internal volume of the case 138 is sealed tothe influent that is coupled to the filter 120 by way of inletconnection 128, except for one or more ports 70 formed in the sidewall140 thereof. Each port 70 includes a check valve for allowing theinfluent to enter into the case 138, but prevents liquid from passing inthe reverse direction. The case 138 can be constructed of differenttypes of plastics or metals to suit the particular needs of thefiltration system. For filtering impurities from water and similarliquids, under low-pressure conditions, the case 138 can be constructedwith a PVC or polyethylene plastic. In this event, the end caps 142 and144 can be bonded, welded or otherwise secured to the cylindricalsidewall 140. Where higher pressures or caustic liquids are employed,such as chemicals to be filtered, the case 138 can be constructed ofstainless steel or other types of materials and welded together.

Disposed within the case 138 of the filter assembly 136 are a pair ofperforated cylinders. An inner perforated cylinder 54 is supportedwithin respective holes formed in the top end cap 142 and the bottom endcap 144. Moreover, the inner perforated cylinder 54 is supported by abottom filter chamber end cap 146. The parts can be bonded, threaded orotherwise fixed together for permanent or removable attachment. Securedaround the outer circumference of the inner perforated cylinder 54 is ascreen mesh 148. The screen mesh can be of a synthetic or metallicmaterial having a porosity sufficiently small to prevent passagetherethrough of the granular particles comprising the porous media orfilter bed. Fixed within the inner perforated cylinder 54 is a plug 64to provide an obstruction so as to prevent liquid passage axially alongthe inner perforated cylinder 54.

As an alternative to the orifice structures 66 described above inconnection with FIGS. 3 and 4, the embodiment of FIG. 8 includes pluralcheck valves, one shown as reference character 150. It is contemplatedthat check valves with orifices will be the preferable structure. Thecheck valves 150 each include a seat, and a ball constructed of asynthetic material so as to be buoyant on the liquids. The check valve150 includes one or more orifices, and will be described in more detailbelow. Nevertheless, the check valves 150 are open during the filtrationoperation, but are generally closed, except for the orifice formedtherein during the backwash operation. In this manner, the restrictionto the fluid flow during the filtration operation is eliminated.

An outer perforated cylinder 60 is fastened at a bottom end thereof tothe filter chamber end cap 146. At the upper end, the outer perforatedcylinder 60 is fixed to an annular-shaped piece 152 and bonded orotherwise fastened to the internal surface of the filter assembly case140. Much like the inner perforated cylinder structure 54, the outerperforated cylinder 60 has attached to the inside surface thereof ascreen mesh 154 that serves the same function as the screen mesh 148.The annular space between the outer perforated cylinder 60 and the innerperforated cylinder 54 defines a filtration chamber 156. The filtrationchamber 156 is filled with a porous media, such as granular particlesfor removing impurities from an influent. Located above the filtrationchamber 156 is the backwash chamber 62. Preferably, the backwash chamberis about the same volume as the filtration chamber 156, although it maybe of a larger volume. As noted in FIG. 8, the backwash chamber 62 has alarger radial dimension than the filtration chamber 156. This differencein radial dimensions is believed to impart a swirling action to thegranular particles 58 as they are lifted from the filtration chamber 156to the backwash chamber 62. The swirling action is believed to agitateand facilitate separation of the particles to free the impuritiestherefrom. Without the difference in the radial dimensions, the tendencyis to lift the entire column of media as a plug:

During a filtration operation, the influent is directed in the followingpath. From the inlet connection 128, the influent is forced into thespace 160 that surrounds the filter assembly case 138. The influent isthen forced into the port 70 via the check valve in the sidewall of thefilter assembly case 138. Once the influent is forced through the checkvalve port 70, it fills the annular chamber 162 and completely surroundsthe outer surface of the outer perforated cylinder 60. The influent thenpasses radially through the porous filter media 58 where the impuritiesare removed. The filtered influent then passes through the perforationsof the inner perforated cylinder 54 and into the internal volume 164 ofthe inner perforated cylinder 54. The filtered influent then passesthrough the opened check valves 150 and exits at the bottom of thefilter 120 to the outlet connection 132. The radial flow aspect allows alarge surface area of the porous media 58 to be exposed to the influent.This process continues until the pressure rises at the inlet of thefilter 120, denoting that the porous media 58 has accumulated asufficient amount of impurities that the filtration process is becominginefficient.

Once it is determined that a backwash operation must be carried out, theappropriate valves are activated, whereby a backwash liquid is forcedinto the connection 132. The flow path of the liquid is effective toremove the impurities from the porous material 58 and carry theimpurities with the backwash liquid out of the filter via the connection128. The backwash liquid is forced into the connection 132 and up intothe central part 164 of the inner perforated cylinder 54. The checkvalves 150 close, except for the small orifices formed therein. In thismanner, the flow of the backwash liquid encounters successively smallerorifices, thereby facilitating the fluidizing of the granular particles,as described above. Each section of the porous media 58 in thefiltration chamber 156 becomes fluidized and carried up into thebackwash chamber 62. In the backwash chamber 62, the swirling andagitation action imparted to the granular particles 58 frees theimpurities therefrom. The impurities flow from the backwash chamber 62into the central area 166 of the inner perforated cylinder 54, and outthe end 168 thereof. It is noted that during the fluidization process,the check valve closes the port 70 in the filter assembly case 138,thereby preventing a substantial flow of the backwash liquid radiallyoutwardly through the outer perforated cylinder 60. In any event, theimpurities carried by the backwash liquid are directed from the top end168 of the inner perforated cylinder 54 into the outer annular area 160,and therefrom to the filter connection 128.

FIG. 9 illustrates one embodiment of the check valves 150 fixed withinthe inner perforated cylinder 54. The check valve 150 is constructedwith a plate 170 having a primary hole 172 that can be plugged with aspherical-shaped ball 174. The ball 174 is preferably constructed of aplastic or similar material that is buoyant. The individual check valveballs may be of different buoyant weights. While not shown, thoseskilled in the art may prefer to maintain the ball 174 within a wirecage, or the like, to prevent the ball from falling downwardly andinadvertently stopping the hole in the check valve plate locatedtherebelow. Also formed within the plate 170 are one or more orifices176 that are not plugged or otherwise stopped by the check valve ball174. The orifices 176 function much like those noted above in connectionwith FIG. 3 and identified as reference numeral 66. Again, thecumulative open area of each of the orifices 176 of one check valveplate 170 are preferably different from that of the other check valveplates fixed within the inner perforated cylinder 58.

FIG. 10 illustrates another embodiment of a check valve plate 180 thatcan be fixed within the inner perforated cylinder 58. Rather than havingthe apertures 176 shown in FIG. 9, the check valve plate 180 of FIG. 10includes a roughened or serrated edge 182 to prevent the ball 174 fromseating in a sealed manner to the plate 180. The irregular-shaped seat182 of the plate 180 allows liquid to pass therethrough even when theball 174 is forced within the hole of the plate 180.

FIGS. 11 and 12 illustrate a check valve that can be employed withinsidewall 140 the filter assembly case 138, and particularly inconnection with the port 70 of FIG. 8. This check valve includes anelastomeric stopper 184 having a planar portion 186 and a stem portion188. Formed at the end of the stem 188 is a conical or enlarged end 190that can be pressed through the anchor hole 183 in one direction duringinstallation, but cannot be easily removed. As noted in FIG. 11, fluidflow in the direction of arrow 192 causes the port holes 70 to be closedby the stopper flap 186, thereby preventing liquid flow through thefilter assembly case 140. In FIG. 12, the liquid flow in the directionof arrow 194 allows fluid to flow through the ports 70. Thus, during thefiltration operation, influent can pass through the ports 70 into thevolume 162 surrounding the outer perforated cylinder 60 (FIG. 8). Whileonly two ports 70 are shown, many more holes can be formed so as to becovered by the elastomeric check valve flapper 186. Other types of checkvalves, such as elastomeric flaps can be fastened along one edge thereofto the inside wall of the filter assembly case 140 to thereby be forcedclosed or opened by the directional flow of liquid, and thereby functionas a check valve. Those skilled in the art may prefer to employ a hostof other types of inlet check valves and inner cylinder check valves inconnection with the filter 120, including mechanical and electricaloperated devices.

FIG. 13 illustrates another embodiment of the radial-flow filterconstructed in accordance with the principles and concepts of theinvention. The filter assembly 200 has structural features similar tothat shown in FIG. 8. With the construction of filter assembly 200,there are shown plural elastomeric O-rings 202 located between the outerperforated cylinder 60 and a cylindrical case 204. While four O-ringsare shown in the embodiment of FIG. 13, any number of O-rings may beutilized. Each O-ring 202 provides a seal between the outer perforatedcylinder 60 and the inner surface of the case 204. The O-rings 202function to change or modify the direction of the liquid flow inside theporous media 56. A substantial amount of the radial flow through theporous media 56 is changed to axial flow. Moreover, additional axialforces are generated within the porous media 56. The use of the O-rings202 may change the number of check valves 150 needed, and indeed mayrequire a leak hole 206 in the sidewall of the case 204. The leak holes206 would be located between each adjacent O-ring 202 in order to allowfor liquid flow in and out of each section of the porous media. As canbe appreciated, the selection of the number of O-rings and the orificesizes in the check valves 150 and the axial lengths of the sections caninsure that adequate axial forces on the porous media 56 exist duringthe backwash operation.

The filter assembly 200 is also shown to include the bladder 100. Thebladder 100 can be used in combination, with or without the orifices inthe check valve 150, as well as the O-rings 202. The bladder 100functions to concentrate substantially all of the backwash liquid flowin the inner perforated cylinder 54 is directed to that area locateddirectly beneath each check valve 150. The bladder 100 maximizes theamount of axial flow that exists in each porous media section. Thebladder 100 is shown with the sidewall deformed inwardly in a concaveshape, due to the fluid pressure exerted on the outer surface thereofduring a filtration cycle.

Lastly, the filter assembly 200 includes a backwash outlet check valve210. The outlet check valve 210 is placed in an non-perforated portionof the inner cylinder 54, preferably near the bottom of the filterassembly 200. When forced to an open condition by the pressure of thebackwash liquid, the outlet check valve 210 provides a flow path fromthe internal volume of the inner cylinder 54 to the annular volume 162that exists between the case 204 and the outer perforated cylinder 60.The outlet check valve 210 allows for the backwash liquid to exit belowthe filtration chamber and be carried directly to the outside annularvolume 162 without first having to pass through the porous media 56.Once entering the outside annular volume 162, the backwash liquid exitsthrough either the leak holes 206 or out into the top backwash chamber62 via the porous media 56.

The outlet check valve 210 also functions to seal the inlet check valves184 closed during backwashing. This is helpful in situations where verysmall granular porous media 56 becomes packed with contaminants andallows small amounts of the backwash liquid to reach the outside annularvolume 162. In addition, the outlet check valve 210 provides backwashliquid to the outside annular volume 162 and assists in the fluidizationof the porous media 56 by the additional liquid diverted inwardly by theO-rings 202 into the porous media 56. It also produces a water scour tothe outside annular volume 162 and significantly reduces the amount ofbackwash liquid required to remove the impurities from the porous media56. This is because the larger impurities lodged in the screen mesh areflushed directly out of the leak holes 206, rather than being carriedback into the porous media 56 and out through the backwash chamber 62.By discharging the larger impurities directly out of the leak holes 206,the particulate matter that would otherwise be too large to enterthrough the outer screen mesh covering the outer perforated cylinder 60is completely removed.

As an alternative, all leak holes but the leak hole 206 at the top canbe eliminated if each O-ring 202 has a vertical channel cut therein toallow the backwash liquid to flow upwardly around each O-ring 202.Moreover, alternatives to the check valves 150 may be devised by thoseskilled in the art, including forming orifices in the bladder 100itself, and allowing a portion of the bladder to block the verticalpassageway in the inner perforated cylinder 54.

As can be seen, the filter assembly 200 of FIG. 13 provides additionalfeatures which may be considered optional, and in some circumstances maybe necessary. Those skilled in the art may find that in many situations,various individual features of the embodiments may be selected so as toproduce optimum filtering and backwash results. Also, while the filtermedia 56 has been described above generally in connection with theremoval of particulate matter or impurities, other types of media can beselected so as to remove dissolved solids, provide coaction betweensolids and fluids, provide coalescing capabilities and even provide acatalyst to the influent supplied to the filter. Nevertheless, thefilter constructed according to the principles and concepts of theinvention provides an increased surface area for the radial flow offluids through the media, whether or not it is used for filteringpurposes, and provides for an efficient backwash for fluidizing themedia.

FIGS. 14 a and 14 b illustrate another embodiment of the radial flowfilter 220, incorporating a perforated bladder 222. The bladder 222 ispreferably made of a flexible elastomeric material suitably constructedto withstand the pressures encountered within the filter, as well as thetype of influent and backwash fluids passed through the filter 220. Thebladder 222 may be constructed as a tubular member. A rigid plate 224functions as the blocking obstruction within the inner perforatedcylinder 54.

Rather than utilizing check valves with orifices or orifice platestructures described above, the bladder 222 includes a pattern ofperforations 226 functioning as orifices. The orifices 226 formed in thebladder 222 adjacent a top section 80 of the filter media 56 functionsto enable fluidization during a backwash cycle. The orifices 226 can belocated annularly around the upper section of the bladder 222.Associated with a second section 82 of the porous media 56, are anadditional set of orifices 228 formed in the bladder 222. Subsequentsets 230-236 of orifices are formed in the bladder 222. The open area ofeach set 226-236 of orifices is larger, as a function of distance awayfrom the plate 224. As such, the sets of orifices function very muchlike that described above in conjunction with the orifice structuresshown in FIGS. 3 and 4. The variation in the open area between the setsof orifices can be accomplished in various ways. For example, the toporifice set 226 can comprise a predefined number of openings having afirst diameter. The second set 228 of orifices can include the samenumber of openings, but of a larger diameter. Each subsequent set230-236 of the orifices can be formed with orifices of successivelylarger diameters. As an alternative, the orifices of the sets can be ofthe same diameter, but ranging from a small number of orificesassociated with set 226, and with larger numbers of orifices as afunction of the distance from the plate 224. Many other arrangements canbe devised by those skilled in the art to achieve an orifice structurethat facilitates the fluidizing of the porous media 56.

It is significant to note that the orifices of the various sets 226-236are fabricated so as to be aligned with respective perforations in theinner perforated cylinder 54. In this manner, the backwash fluid isallowed to flow through both the orifices of the bladder 222 and theperforations in the inner perforated cylinder 54, into the porous media56. With regard to the bottom set 236 of orifices, they aresubstantially large so as to pass the filtered influent therethroughwithout creating a pressure differential thereacross.

FIG. 14 a illustrates the radial flow filter assembly 220 during thefilter cycle. During such cycle, the influent enters the assembly 220 inthe direction of arrow 240 and enters the column of the porous media 56at the top thereof. However, a majority of the influent passes throughthe opened check valves 184 and flows radially through the respectivesections of the porous media 56. Each section is separated by arespective O-ring 202 for facilitating fluidization during the backwashcycle. Because of the pressure of the filtered influent passing radiallythrough the media 56, the sidewall of the bladder 222 is forcedinwardly, as shown in FIG. 14 a. While some of the filtered influentpasses through the various sets of orifices during the filtration cycle,a majority of the influent passes through the set of large orifices 236and out of the filter assembly, shown by arrow 242.

FIG. 14 b illustrates the filter assembly 220 during a backwash cycle.During the backwash cycle, the backwash fluid enters the assembly in thedirection of arrow 244. The backwash liquid enters the inner volume ofthe bladder 222, thus pressing it against the inside surface of theinner perforated cylinder 54. The backwash liquid is forced through thesets of orifices, as noted by arrows 246. The backwash fluid then flowsinto the porous media 66 for fluidization thereof in the manner notedabove. The check valves 184 are closed during the backwash cycle forfacilitating sequential fluidization of the various sections of theporous media 56. The backwash fluid carries the impurities and thereleased particles out of the filter assembly 220 in the direction notedby arrow 248.

FIGS. 15 a and 15 b illustrate another embodiment of the radial-flowfilter that operates in an inverted manner. This embodiment isparticularly well suited for use with granular beads that are eitherlarge or generally lightweight. In the filter cycle, as shown in FIG. 15a, a porous media setting liquid, which is preferably not the influent,is pumped into the filter assembly 250 in the direction of arrow 252.The drag forces imparted from the setting fluid to the porous media 56cause the beads to be lifted upwardly into the top portion of the filterchamber. Each check valve 150 fixed within the inner perforated cylinder54 in the backwash chamber 62 is closed, while the check valves 150situated in the filtration chamber are opened. Once the porous media 56is lifted into the filtration chamber by the setting liquid, a valvingarrangement (not shown) is actuated to thereby allow the influent topass into the filter assembly 250 in the direction noted by arrow 252.Moreover, the influent is allowed to pass through the open inlet checkvalves 184 in the direction of arrows 254. The influent passes radiallythrough the media 56 and into the internal volume of the innerperforated cylinder 54, via the opened check valves 150. The filteredinfluent then exits the assembly 250 in the direction noted by arrow256.

FIG. 15 b illustrates the inverted filter assembly 250 during a backwashcycle. In the backwash cycle, the porous media 56 is simply allowed tosettle by way of gravity into the chamber located at the bottom of theassembly. During the movement of the filter media 56 from the upperfiltration chamber to the lower backwash chamber, the granular particlesare separated and the impurities are removed therefrom. The particulatematter and impurities pass through the open check valves within thelower portion of the inner perforated cylinder 54 and are carried out ofthe assembly 250 by the backwash liquid, in the direction of arrow 260.In the event that the column of the porous media 56 is not moveddownwardly by the force of gravity, the backwash liquid entering theassembly 250 in the direction of arrow 262 causes sequentialfluidization of the sections in the manner described above.

While the preferred and other embodiments of the invention have beendisclosed with reference to a specific radial-flow filter, it is to beunderstood that many changes in detail may be made as a matter ofengineering choices, without departing from the spirit and scope of theinvention, as defined by the appended claims. Indeed, those skilled inthe art may prefer to utilize only certain features of the invention, orutilize various features from the different embodiments to achieve theindividual or combined advantages thereof.

1. A method of treating an influent with a treatment device, comprisingthe steps of: passing the influent radially inwardly through a porousmedia to treat the influent, and passing the treated influent radiallyinto an internal volume that is surrounded by said porous media, andthen passing the treated influent axially in said internal volume in afirst direction to an outlet; preventing the porous media from enteringsaid internal volume; passing a pressurized backwash fluid axially insaid internal volume in a second direction, opposite said firstdirection; using an orifice restriction located within said internalvolume to define respective upper and lower portions of said internalvolume; forcing the pressurized backwash fluid into said internal volumeso that a portion of the pressurized backwash fluid is forced throughsaid orifice and into the upper portion of the internal volume and intothe porous media to create a drag force on an upper portion of theporous media, and a remainder of the pressurized backwash fluid in thelower portion of said internal volume is forced into the porous mediaand thereby bypasses said orifice, whereby a drag force is imparted on alower portion of the porous media; and fluidizing respective portions ofthe porous media when the drag force exerted thereon by the pressurizedbackwash fluid is greater than a buoyant weight of the respectiveportion of the porous media.
 2. The method of claim 1, further includingtreating the influent by filtering impurities therefrom; coupling thetreated influent from said treatment device to downline equipment; anddetecting a pressure rise in the influent coupled to said treatmentdevice to determine if said porous media has accumulated a sufficientamount of impurities.
 3. The method of claim 1, further includingbackwashing the treatment device by passing the pressurized backwashfluid into the lower portion of said internal volume of the treatmentdevice, then passing a portion of the backwash fluid through saidorifice in the upper portion of said internal volume and radiallyoutwardly into the porous media.
 4. The method of claim 1, furtherincluding backwashing the porous media by sectional fluidization thereofusing a plurality of said orifices to define a plurality of portions ofsaid internal volume.
 5. The method of claim 4, further includingarranging the orifices axially in said internal volume, and wherein theorifice open areas are sequentially smaller.
 6. The method of claim 1,further including passing the backwash fluid serially through pluralspaced apart orifices in said internal volume which is verticallyoriented, and fluidizing the porous media from a top thereof to a bottomthereof.
 7. The method of claim 1, further including fully blocking anaxial flow of the backwash fluid in an uppermost portion of saidinternal volume above a topmost orifice by a blockage in said innervolume.
 8. The method of claim 7, further including forming the internalvolume using a perforated tubular member with a blocking plate fixedtherein in said internal volume, wherein said blocking plate defines atop internal volume of said perforated tubular member and a bottominternal volume of said perforated tubular member.
 9. The method ofclaim 8, further including using a bottom annular space around a bottomportion of said perforated tubular member to contain said porous mediaduring treatment thereof when the treatment fluid passes radiallyinwardly therethrough, and using a top annular space around a topportion of said perforated tubular member to which fluidized porousmedia is carried.
 10. The method of claim 9, further including formingthe blockage in said internal volume laterally adjacent a locationbetween said top and bottom annular space around said perforated tubularmember.
 11. The method of claim 9, further including passing thebackwash fluid upwardly in said bottom internal volume and upwardlythrough said orifice, then passing the backwash fluid radially outwardlythough said perforated tubular member into said bottom annular space tofluidize a portion of the porous media, then passing the backwash fluidupwardly into said top annular space with fluidized porous media, andthen passing the backwash fluid into the top internal volume of saidperforated tubular member.
 12. A method of treating an influent,comprising the steps of: using an inner perforated member and an outerperforated member to contain a porous media therebetween, and passing aninfluent to be treated radially inwardly through said porous media sothat the treated influent enters an internal volume of said innerperforated member; using an upper annular space around an upper portionof said inner perforated member as a fluidizing chamber to whichfluidized porous media is carried; passing a portion of the influentaxially downwardly in said upper annular space to cause the porous mediato settle downwardly; passing a backwash fluid upwardly in a bottomportion of said inner perforated member and through an orifice to causefluidization of a portion of the porous media located between said innerperforated member and said outer perforated member, said fluidizedporous media carried to said fluidizing chamber; and passing thebackwash fluid to the fluidizing chamber and back into a top portion ofsaid inner perforated member.
 13. The method of claim 12, furtherincluding blocking passage of the backwash fluid in said innerperforated member with a blocking plate to prevent passage of thebackwash fluid from a bottom portion of the inner perforated memberthrough the internal volume and to the top portion of the innerperforated member.
 14. The method of claim 13, further includingpreventing fluidized porous media from entering into an internal volumeof the top portion of the inner perforated member.